
<!DOCTYPE html>
<html lang="en" class="RFC">
<head>
<meta charset="utf-8">
<meta content="Common,Latin" name="scripts">
<meta content="initial-scale=1.0" name="viewport">
<title>RFC 8740: Using TLS 1.3 with HTTP/2</title>
<meta content="David Benjamin" name="author">
<meta content="
       This document updates RFC 7540 by forbidding TLS 1.3 post-handshake
authentication, as an analog to the existing TLS 1.2 renegotiation restriction. 
    " name="description">
<meta content="xml2rfc 2.40.0" name="generator">
<meta content="HTTP" name="keyword">
<meta content="renegotiation" name="keyword">
<meta content="post-handshake client authentication" name="keyword">
<meta content="8740" name="rfc.number">
<link href="rfc8740.xml" rel="alternate" type="application/rfc+xml">
<link href="#copyright" rel="license">
<style type="text/css">/*

  NOTE: Changes at the bottom of this file overrides some earlier settings.

  Once the style has stabilized and has been adopted as an official RFC style,
  this can be consolidated so that style settings occur only in one place, but
  for now the contents of this file consists first of the initial CSS work as
  provided to the RFC Formatter (xml2rfc) work, followed by itemized and
  commented changes found necssary during the development of the v3
  formatters.

*/

/* fonts */
@import url('https://fonts.googleapis.com/css?family=Noto+Sans'); /* Sans-serif */
@import url('https://fonts.googleapis.com/css?family=Noto+Serif'); /* Serif (print) */
@import url('https://fonts.googleapis.com/css?family=Roboto+Mono'); /* Monospace */

@viewport {
  zoom: 1.0;
  width: extend-to-zoom;
}
@-ms-viewport {
  width: extend-to-zoom;
  zoom: 1.0;
}
/* general and mobile first */
html {
}
body {
  max-width: 90%;
  margin: 1.5em auto;
  color: #222;
  background-color: #fff;
  font-size: 14px;
  font-family: 'Noto Sans', Arial, Helvetica, sans-serif;
  line-height: 1.6;
  scroll-behavior: smooth;
}
.ears {
  display: none;
}

/* headings */
#title, h1, h2, h3, h4, h5, h6 {
  margin: 1em 0 0.5em;
  font-weight: bold;
  line-height: 1.3;
}
#title {
  clear: both;
  border-bottom: 1px solid #ddd;
  margin: 0 0 0.5em 0;
  padding: 1em 0 0.5em;
}
.author {
  padding-bottom: 4px;
}
h1 {
  font-size: 26px;
  margin: 1em 0;
}
h2 {
  font-size: 22px;
  margin-top: -20px;  /* provide offset for in-page anchors */
  padding-top: 33px;
}
h3 {
  font-size: 18px;
  margin-top: -36px;  /* provide offset for in-page anchors */
  padding-top: 42px;
}
h4 {
  font-size: 16px;
  margin-top: -36px;  /* provide offset for in-page anchors */
  padding-top: 42px;
}
h5, h6 {
  font-size: 14px;
}
#n-copyright-notice {
  border-bottom: 1px solid #ddd;
  padding-bottom: 1em;
  margin-bottom: 1em;
}
/* general structure */
p {
  padding: 0;
  margin: 0 0 1em 0;
  text-align: left;
}
div, span {
  position: relative;
}
div {
  margin: 0;
}
.alignRight.art-text {
  background-color: #f9f9f9;
  border: 1px solid #eee;
  border-radius: 3px;
  padding: 1em 1em 0;
  margin-bottom: 1.5em;
}
.alignRight.art-text pre {
  padding: 0;
}
.alignRight {
  margin: 1em 0;
}
.alignRight > *:first-child {
  border: none;
  margin: 0;
  float: right;
  clear: both;
}
.alignRight > *:nth-child(2) {
  clear: both;
  display: block;
  border: none;
}
svg {
  display: block;
}
.alignCenter.art-text {
  background-color: #f9f9f9;
  border: 1px solid #eee;
  border-radius: 3px;
  padding: 1em 1em 0;
  margin-bottom: 1.5em;
}
.alignCenter.art-text pre {
  padding: 0;
}
.alignCenter {
  margin: 1em 0;
}
.alignCenter > *:first-child {
  border: none;
  /* this isn't optimal, but it's an existence proof.  PrinceXML doesn't
     support flexbox yet.
  */
  display: table;
  margin: 0 auto;
}

/* lists */
ol, ul {
  padding: 0;
  margin: 0 0 1em 2em;
}
ol ol, ul ul, ol ul, ul ol {
  margin-left: 1em;
}
li {
  margin: 0 0 0.25em 0;
}
.ulCompact li {
  margin: 0;
}
ul.empty, .ulEmpty {
  list-style-type: none;
}
ul.empty li, .ulEmpty li {
  margin-top: 0.5em;
}
ul.compact, .ulCompact,
ol.compact, .olCompact {
  line-height: 100%;
  margin: 0 0 0 2em;
}

/* definition lists */
dl {
}
dl > dt {
  float: left;
  margin-right: 1em;
}
/* 
dl.nohang > dt {
  float: none;
}
*/
dl > dd {
  margin-bottom: .8em;
  min-height: 1.3em;
}
dl.compact > dd, .dlCompact > dd {
  margin-bottom: 0em;
}
dl > dd > dl {
  margin-top: 0.5em;
  margin-bottom: 0em;
}

/* links */
a {
  text-decoration: none;
}
a[href] {
  color: #22e; /* Arlen: WCAG 2019 */
}
a[href]:hover {
  background-color: #f2f2f2;
}
figcaption a[href],
a[href].selfRef {
  color: #222;
}
/* XXX probably not this:
a.selfRef:hover {
  background-color: transparent;
  cursor: default;
} */

/* Figures */
tt, code, pre, code {
  background-color: #f9f9f9;
  font-family: 'Roboto Mono', monospace;
}
pre {
  border: 1px solid #eee;
  margin: 0;
  padding: 1em;
}
img {
  max-width: 100%;
}
figure {
  margin: 0;
}
figure blockquote {
  margin: 0.8em 0.4em 0.4em;
}
figcaption {
  font-style: italic;
  margin: 0 0 1em 0;
}
@media screen {
  pre {
    overflow-x: auto;
    max-width: 100%;
    max-width: calc(100% - 22px);
  }
}

/* aside, blockquote */
aside, blockquote {
  margin-left: 0;
  padding: 1.2em 2em;
}
blockquote {
  background-color: #f9f9f9;
  color: #111; /* Arlen: WCAG 2019 */
  border: 1px solid #ddd;
  border-radius: 3px;
  margin: 1em 0;
}
cite {
  display: block;
  text-align: right;
  font-style: italic;
}

/* tables */
table {
  width: 100%;
  margin: 0 0 1em;
  border-collapse: collapse;
  border: 1px solid #eee;
}
th, td {
  text-align: left;
  vertical-align: top;
  padding: 0.5em 0.75em;
}
th {
  text-align: left;
  background-color: #e9e9e9;
}
tr:nth-child(2n+1) > td {
  background-color: #f5f5f5;
}
table caption {
  font-style: italic;
  margin: 0;
  padding: 0;
  text-align: left;
}
table p {
  /* XXX to avoid bottom margin on table row signifiers. If paragraphs should
     be allowed within tables more generally, it would be far better to select on a class. */
  margin: 0;
}

/* pilcrow */
a.pilcrow {
  color: #666; /* Arlen: AHDJ 2019 */
  text-decoration: none;
  visibility: hidden;
  user-select: none;
  -ms-user-select: none;
  -o-user-select:none;
  -moz-user-select: none;
  -khtml-user-select: none;
  -webkit-user-select: none;
  -webkit-touch-callout: none;
}
@media screen {
  aside:hover > a.pilcrow,
  p:hover > a.pilcrow,
  blockquote:hover > a.pilcrow,
  div:hover > a.pilcrow,
  li:hover > a.pilcrow,
  pre:hover > a.pilcrow {
    visibility: visible;
  }
  a.pilcrow:hover {
    background-color: transparent;
  }
}

/* misc */
hr {
  border: 0;
  border-top: 1px solid #eee;
}
.bcp14 {
  font-variant: small-caps;
}

.role {
  font-variant: all-small-caps;
}

/* info block */
#identifiers {
  margin: 0;
  font-size: 0.9em;
}
#identifiers dt {
  width: 3em;
  clear: left;
}
#identifiers dd {
  float: left;
  margin-bottom: 0;
}
#identifiers .authors .author {
  display: inline-block;
  margin-right: 1.5em;
}
#identifiers .authors .org {
  font-style: italic;
}

/* The prepared/rendered info at the very bottom of the page */
.docInfo {
  color: #666; /* Arlen: WCAG 2019 */
  font-size: 0.9em;
  font-style: italic;
  margin-top: 2em;
}
.docInfo .prepared {
  float: left;
}
.docInfo .prepared {
  float: right;
}

/* table of contents */
#toc  {
  padding: 0.75em 0 2em 0;
  margin-bottom: 1em;
}
nav.toc ul {
  margin: 0 0.5em 0 0;
  padding: 0;
  list-style: none;
}
nav.toc li {
  line-height: 1.3em;
  margin: 0.75em 0;
  padding-left: 1.2em;
  text-indent: -1.2em;
}
/* references */
.references dt {
  text-align: right;
  font-weight: bold;
  min-width: 7em;
}
.references dd {
  margin-left: 8em;
  overflow: auto;
}

.refInstance {
  margin-bottom: 1.25em;
}

.references .ascii {
  margin-bottom: 0.25em;
}

/* index */
.index ul {
  margin: 0 0 0 1em;
  padding: 0;
  list-style: none;
}
.index ul ul {
  margin: 0;
}
.index li {
  margin: 0;
  text-indent: -2em;
  padding-left: 2em;
  padding-bottom: 5px;
}
.indexIndex {
  margin: 0.5em 0 1em;
}
.index a {
  font-weight: 700;
}
/* make the index two-column on all but the smallest screens */
@media (min-width: 600px) {
  .index ul {
    -moz-column-count: 2;
    -moz-column-gap: 20px;
  }
  .index ul ul {
    -moz-column-count: 1;
    -moz-column-gap: 0;
  }
}

/* authors */
address.vcard {
  font-style: normal;
  margin: 1em 0;
}

address.vcard .nameRole {
  font-weight: 700;
  margin-left: 0;
}
address.vcard .label {
  font-family: "Noto Sans",Arial,Helvetica,sans-serif;
  margin: 0.5em 0;
}
address.vcard .type {
  display: none;
}
.alternative-contact {
  margin: 1.5em 0 1em;
}
hr.addr {
  border-top: 1px dashed;
  margin: 0;
  color: #ddd;
  max-width: calc(100% - 16px);
}

/* temporary notes */
.rfcEditorRemove::before {
  position: absolute;
  top: 0.2em;
  right: 0.2em;
  padding: 0.2em;
  content: "The RFC Editor will remove this note";
  color: #9e2a00; /* Arlen: WCAG 2019 */
  background-color: #ffd; /* Arlen: WCAG 2019 */
}
.rfcEditorRemove {
  position: relative;
  padding-top: 1.8em;
  background-color: #ffd; /* Arlen: WCAG 2019 */
  border-radius: 3px;
}
.cref {
  background-color: #ffd; /* Arlen: WCAG 2019 */
  padding: 2px 4px;
}
.crefSource {
  font-style: italic;
}
/* alternative layout for smaller screens */
@media screen and (max-width: 1023px) {
  body {
    padding-top: 2em;
  }
  #title {
    padding: 1em 0;
  }
  h1 {
    font-size: 24px;
  }
  h2 {
    font-size: 20px;
    margin-top: -18px;  /* provide offset for in-page anchors */
    padding-top: 38px;
  }
  #identifiers dd {
    max-width: 60%;
  }
  #toc {
    position: fixed;
    z-index: 2;
    top: 0;
    right: 0;
    padding: 0;
    margin: 0;
    background-color: inherit;
    border-bottom: 1px solid #ccc;
  }
  #toc h2 {
    margin: -1px 0 0 0;
    padding: 4px 0 4px 6px;
    padding-right: 1em;
    min-width: 190px;
    font-size: 1.1em;
    text-align: right;
    background-color: #444;
    color: white;
    cursor: pointer;
  }
  #toc h2::before { /* css hamburger */
    float: right;
    position: relative;
    width: 1em;
    height: 1px;
    left: -164px;
    margin: 6px 0 0 0;
    background: white none repeat scroll 0 0;
    box-shadow: 0 4px 0 0 white, 0 8px 0 0 white;
    content: "";
  }
  #toc nav {
    display: none;
    padding: 0.5em 1em 1em;
    overflow: auto;
    height: calc(100vh - 48px);
    border-left: 1px solid #ddd;
  }
}

/* alternative layout for wide screens */
@media screen and (min-width: 1024px) {
  body {
    max-width: 724px;
    margin: 42px auto;
    padding-left: 1.5em;
    padding-right: 29em;
  }
  #toc {
    position: fixed;
    top: 42px;
    right: 42px;
    width: 25%;
    margin: 0;
    padding: 0 1em;
    z-index: 1;
  }
  #toc h2 {
    border-top: none;
    border-bottom: 1px solid #ddd;
    font-size: 1em;
    font-weight: normal;
    margin: 0;
    padding: 0.25em 1em 1em 0;
  }
  #toc nav {
    display: block;
    height: calc(90vh - 84px);
    bottom: 0;
    padding: 0.5em 0 0;
    overflow: auto;
  }
  img { /* future proofing */
    max-width: 100%;
    height: auto;
  }
}

/* pagination */
@media print {
  body {

    width: 100%;
  }
  p {
    orphans: 3;
    widows: 3;
  }
  #n-copyright-notice {
    border-bottom: none;
  }
  #toc, #n-introduction {
    page-break-before: always;
  }
  #toc {
    border-top: none;
    padding-top: 0;
  }
  figure, pre {
    page-break-inside: avoid;
  }
  figure {
    overflow: scroll;
  }
  h1, h2, h3, h4, h5, h6 {
    page-break-after: avoid;
  }
  h2+*, h3+*, h4+*, h5+*, h6+* {
    page-break-before: avoid;
  }
  pre {
    white-space: pre-wrap;
    word-wrap: break-word;
    font-size: 10pt;
  }
  table {
    border: 1px solid #ddd;
  }
  td {
    border-top: 1px solid #ddd;
  }
}

/* This is commented out here, as the string-set: doesn't
   pass W3C validation currently */
/*
.ears thead .left {
  string-set: ears-top-left content();
}

.ears thead .center {
  string-set: ears-top-center content();
}

.ears thead .right {
  string-set: ears-top-right content();
}

.ears tfoot .left {
  string-set: ears-bottom-left content();
}

.ears tfoot .center {
  string-set: ears-bottom-center content();
}

.ears tfoot .right {
  string-set: ears-bottom-right content();
}
*/

@page :first {
  padding-top: 0;
  @top-left {
    content: normal;
    border: none;
  }
  @top-center {
    content: normal;
    border: none;
  }
  @top-right {
    content: normal;
    border: none;
  }
}

@page {
  size: A4;
  margin-bottom: 45mm;
  padding-top: 20px;
  /* The follwing is commented out here, but set appropriately by in code, as
     the content depends on the document */
  /*
  @top-left {
    content: 'Internet-Draft';
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @top-left {
    content: string(ears-top-left);
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @top-center {
    content: string(ears-top-center);
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @top-right {
    content: string(ears-top-right);
    vertical-align: bottom;
    border-bottom: solid 1px #ccc;
  }
  @bottom-left {
    content: string(ears-bottom-left);
    vertical-align: top;
    border-top: solid 1px #ccc;
  }
  @bottom-center {
    content: string(ears-bottom-center);
    vertical-align: top;
    border-top: solid 1px #ccc;
  }
  @bottom-right {
      content: '[Page ' counter(page) ']';
      vertical-align: top;
      border-top: solid 1px #ccc;
  }
  */

}

/* Changes introduced to fix issues found during implementation */
/* Make sure links are clickable even if overlapped by following H* */
a {
  z-index: 2;
}
/* Separate body from document info even without intervening H1 */
section {
  clear: both;
}


/* Top align author divs, to avoid names without organization dropping level with org names */
.author {
  vertical-align: top;
}

/* Leave room in document info to show Internet-Draft on one line */
#identifiers dt {
  width: 8em;
}

/* Don't waste quite as much whitespace between label and value in doc info */
#identifiers dd {
  margin-left: 1em;
}

/* Give floating toc a background color (needed when it's a div inside section */
#toc {
  background-color: white;
}

/* Make the collapsed ToC header render white on gray also when it's a link */
@media screen and (max-width: 1023px) {
  #toc h2 a,
  #toc h2 a:link,
  #toc h2 a:focus,
  #toc h2 a:hover,
  #toc a.toplink,
  #toc a.toplink:hover {
    color: white;
    background-color: #444;
    text-decoration: none;
  }
}

/* Give the bottom of the ToC some whitespace */
@media screen and (min-width: 1024px) {
  #toc {
    padding: 0 0 1em 1em;
  }
}

/* Style section numbers with more space between number and title */
.section-number {
  padding-right: 0.5em;
}

/* prevent monospace from becoming overly large */
tt, code, pre, code {
  font-size: 95%;
}

/* Fix the height/width aspect for ascii art*/
pre.sourcecode,
.art-text pre {
  line-height: 1.12;
}


/* Add styling for a link in the ToC that points to the top of the document */
a.toplink {
  float: right;
  margin-right: 0.5em;
}

/* Fix the dl styling to match the RFC 7992 attributes */
dl > dt,
dl.dlParallel > dt {
  float: left;
  margin-right: 1em;
}
dl.dlNewline > dt {
  float: none;
}

/* Provide styling for table cell text alignment */
table td.text-left,
table th.text-left {
  text-align: left;
}
table td.text-center,
table th.text-center {
  text-align: center;
}
table td.text-right,
table th.text-right {
  text-align: right;
}

/* Make the alternative author contact informatio look less like just another
   author, and group it closer with the primary author contact information */
.alternative-contact {
  margin: 0.5em 0 0.25em 0;
}
address .non-ascii {
  margin: 0 0 0 2em;
}

/* With it being possible to set tables with alignment
  left, center, and right, { width: 100%; } does not make sense */
table {
  width: auto;
}

/* Avoid reference text that sits in a block with very wide left margin,
   because of a long floating dt label.*/
.references dd {
  overflow: visible;
}

/* Control caption placement */
caption {
  caption-side: bottom;
}

/* Limit the width of the author address vcard, so names in right-to-left
   script don't end up on the other side of the page. */

address.vcard {
  max-width: 30em;
  margin-right: auto;
}

/* For address alignment dependent on LTR or RTL scripts */
address div.left {
  text-align: left;
}
address div.right {
  text-align: right;
}

/* Provide table alignment support.  We can't use the alignX classes above
   since they do unwanted things with caption and other styling. */
table.right {
 margin-left: auto;
 margin-right: 0;
}
table.center {
 margin-left: auto;
 margin-right: auto;
}
table.left {
 margin-left: 0;
 margin-right: auto;
}

/* Give the table caption label the same styling as the figcaption */
caption a[href] {
  color: #222;
}

@media print {
  .toplink {
    display: none;
  }

  /* avoid overwriting the top border line with the ToC header */
  #toc {
    padding-top: 1px;
  }

  /* Avoid page breaks inside dl and author address entries */
  .vcard {
    page-break-inside: avoid;
  }

}
/* Avoid wrapping of URLs in references */
@media screen {
  .references a {
    white-space: nowrap;
  }
}
/* Tweak the bcp14 keyword presentation */
.bcp14 {
  font-variant: small-caps;
  font-weight: bold;
  font-size: 0.9em;
}
/* Tweak the invisible space above H* in order not to overlay links in text above */
 h2 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 31px;
 }
 h3 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
 h4 {
  margin-top: -18px;  /* provide offset for in-page anchors */
  padding-top: 24px;
 }
/* Float artwork pilcrow to the right */
@media screen {
  .artwork a.pilcrow {
    display: block;
    line-height: 0.7;
    margin-top: 0.15em;
  }
}
/* Make pilcrows on dd visible */
@media screen {
  dd:hover > a.pilcrow {
    visibility: visible;
  }
}
/* Make the placement of figcaption match that of a table's caption
   by removing the figure's added bottom margin */
.alignLeft.art-text,
.alignCenter.art-text,
.alignRight.art-text {
   margin-bottom: 0;
}
.alignLeft,
.alignCenter,
.alignRight {
  margin: 1em 0 0 0;
}
/* In print, the pilcrow won't show on hover, so prevent it from taking up space,
   possibly even requiring a new line */
@media print {
  a.pilcrow {
    display: none;
  }
}
/* Styling for the external metadata */
div#external-metadata {
  background-color: #eee;
  padding: 0.5em;
  margin-bottom: 0.5em;
  display: none;
}
div#internal-metadata {
  padding: 0.5em;                       /* to match the external-metadata padding */
}
/* Styling for title RFC Number */
h1#rfcnum {
  clear: both;
  margin: 0 0 -1em;
  padding: 1em 0 0 0;
}
/* Make .olPercent look the same as <ol><li> */
dl.olPercent > dd {
  margin: 0 0 0.25em 0;
  min-height: initial;
}
/* Give aside some styling to set it apart */
aside {
  border-left: 1px solid #ddd;
  margin: 1em 0 1em 2em;
  padding: 0.2em 2em;
}
aside > dl,
aside > ol,
aside > ul,
aside > table,
aside > p {
  margin-bottom: 0.5em;
}
/* Additional page break settings */
@media print {
  figcaption, table caption {
    page-break-before: avoid;
  }
}
/* Font size adjustments for print */
@media print {
  body  { font-size: 10pt;      line-height: normal; max-width: 96%; }
  h1    { font-size: 1.72em;    padding-top: 1.5em; } /* 1*1.2*1.2*1.2 */
  h2    { font-size: 1.44em;    padding-top: 1.5em; } /* 1*1.2*1.2 */
  h3    { font-size: 1.2em;     padding-top: 1.5em; } /* 1*1.2 */
  h4    { font-size: 1em;       padding-top: 1.5em; }
  h5, h6 { font-size: 1em;      margin: initial; padding: 0.5em 0 0.3em; }
}
/* Sourcecode margin in print, when there's no pilcrow */
@media print {
  .artwork,
  .sourcecode {
    margin-bottom: 1em;
  }
}
/*
  The margin-left: 0 on <dd> removes all distinction
  between levels from nested <dl>s.  Undo that.
*/
dl.olPercent > dd,
dd {
  margin-left: revert;
}
/* Avoid narrow tables forcing too narrow table captions, which may render badly */
table {
  min-width: 20em;
}
/* ol type a */
ol.type-a { list-style-type: lower-alpha; }
ol.type-A { list-style-type: upper-alpha; }
ol.type-i { list-style-type: lower-roman; }
ol.type-I { list-style-type: lower-roman; }
</style>
<link href="rfc-local.css" rel="stylesheet" type="text/css">
<link href="https://dx.doi.org/10.17487/rfc8740" rel="alternate">
  <link href="urn:issn:2070-1721" rel="alternate">
  <link href="https://datatracker.ietf.org/doc/draft-ietf-httpbis-http2-tls13-03" rel="prev">
  </head>
<body>
<script src="https://www.rfc-editor.org/js/metadata.min.js"></script>
<table class="ears">
<thead><tr>
<td class="left">RFC 8740</td>
<td class="center">Using TLS 1.3 with HTTP/2</td>
<td class="right">February 2020</td>
</tr></thead>
<tfoot><tr>
<td class="left">Benjamin</td>
<td class="center">Standards Track</td>
<td class="right">[Page]</td>
</tr></tfoot>
</table>
<div id="external-metadata" class="document-information"></div>
<div id="internal-metadata" class="document-information">
<dl id="identifiers">
<dt class="label-stream">Stream:</dt>
<dd class="stream">Internet Engineering Task Force (IETF)</dd>
<dt class="label-rfc">RFC:</dt>
<dd class="rfc"><a href="https://www.rfc-editor.org/rfc/rfc8740" class="eref">8740</a></dd>
<dt class="label-updates">Updates:</dt>
<dd class="updates">
<a href="https://www.rfc-editor.org/rfc/rfc7540" class="eref">7540</a> </dd>
<dt class="label-category">Category:</dt>
<dd class="category">Standards Track</dd>
<dt class="label-published">Published:</dt>
<dd class="published">
<time datetime="2020-02" class="published">February 2020</time>
    </dd>
<dt class="label-issn">ISSN:</dt>
<dd class="issn">2070-1721</dd>
<dt class="label-authors">Author:</dt>
<dd class="authors">
<div class="author">
      <div class="author-name">D. Benjamin</div>
<div class="org">Google LLC</div>
</div>
</dd>
</dl>
</div>
<h1 id="rfcnum">RFC 8740</h1>
<h1 id="title">Using TLS 1.3 with HTTP/2</h1>
<section id="section-abstract">
      <h2 id="abstract"><a href="#abstract" class="selfRef">Abstract</a></h2>
<p id="section-abstract-1">This document updates RFC 7540 by forbidding TLS 1.3 post-handshake
authentication, as an analog to the existing TLS 1.2 renegotiation restriction.<a href="#section-abstract-1" class="pilcrow">¶</a></p>
</section>
<div id="status-of-memo">
<section id="section-boilerplate.1">
        <h2 id="name-status-of-this-memo">
<a href="#name-status-of-this-memo" class="section-name selfRef">Status of This Memo</a>
        </h2>
<p id="section-boilerplate.1-1">
            This is an Internet Standards Track document.<a href="#section-boilerplate.1-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-2">
            This document is a product of the Internet Engineering Task Force
            (IETF).  It represents the consensus of the IETF community.  It has
            received public review and has been approved for publication by
            the Internet Engineering Steering Group (IESG).  Further
            information on Internet Standards is available in Section 2 of 
            RFC 7841.<a href="#section-boilerplate.1-2" class="pilcrow">¶</a></p>
<p id="section-boilerplate.1-3">
            Information about the current status of this document, any
            errata, and how to provide feedback on it may be obtained at
            <span><a href="https://www.rfc-editor.org/info/rfc8740">https://www.rfc-editor.org/info/rfc8740</a></span>.<a href="#section-boilerplate.1-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="copyright">
<section id="section-boilerplate.2">
        <h2 id="name-copyright-notice">
<a href="#name-copyright-notice" class="section-name selfRef">Copyright Notice</a>
        </h2>
<p id="section-boilerplate.2-1">
            Copyright (c) 2020 IETF Trust and the persons identified as the
            document authors. All rights reserved.<a href="#section-boilerplate.2-1" class="pilcrow">¶</a></p>
<p id="section-boilerplate.2-2">
            This document is subject to BCP 78 and the IETF Trust's Legal
            Provisions Relating to IETF Documents
            (<span><a href="https://trustee.ietf.org/license-info">https://trustee.ietf.org/license-info</a></span>) in effect on the date of
            publication of this document. Please review these documents
            carefully, as they describe your rights and restrictions with
            respect to this document. Code Components extracted from this
            document must include Simplified BSD License text as described in
            Section 4.e of the Trust Legal Provisions and are provided without
            warranty as described in the Simplified BSD License.<a href="#section-boilerplate.2-2" class="pilcrow">¶</a></p>
</section>
</div>
<div id="toc">
<section id="section-toc.1">
        <a href="#" onclick="scroll(0,0)" class="toplink">▲</a><h2 id="name-table-of-contents">
<a href="#name-table-of-contents" class="section-name selfRef">Table of Contents</a>
        </h2>
<nav class="toc"><ul class="toc ulEmpty">
<li class="toc ulEmpty" id="section-toc.1-1.1">
            <p id="section-toc.1-1.1.1"><a href="#section-1" class="xref">1</a>.  <a href="#name-introduction" class="xref">Introduction</a><a href="#section-toc.1-1.1.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.2">
            <p id="section-toc.1-1.2.1"><a href="#section-2" class="xref">2</a>.  <a href="#name-requirements-language" class="xref">Requirements Language</a><a href="#section-toc.1-1.2.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.3">
            <p id="section-toc.1-1.3.1"><a href="#section-3" class="xref">3</a>.  <a href="#name-post-handshake-authenticati" class="xref">Post-Handshake Authentication in HTTP/2</a><a href="#section-toc.1-1.3.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.4">
            <p id="section-toc.1-1.4.1"><a href="#section-4" class="xref">4</a>.  <a href="#name-other-post-handshake-tls-me" class="xref">Other Post-Handshake TLS Messages in HTTP/2</a><a href="#section-toc.1-1.4.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.5">
            <p id="section-toc.1-1.5.1"><a href="#section-5" class="xref">5</a>.  <a href="#name-security-considerations" class="xref">Security Considerations</a><a href="#section-toc.1-1.5.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.6">
            <p id="section-toc.1-1.6.1"><a href="#section-6" class="xref">6</a>.  <a href="#name-iana-considerations" class="xref">IANA Considerations</a><a href="#section-toc.1-1.6.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.7">
            <p id="section-toc.1-1.7.1"><a href="#section-7" class="xref">7</a>.  <a href="#name-references" class="xref">References</a><a href="#section-toc.1-1.7.1" class="pilcrow">¶</a></p>
<ul class="toc ulEmpty">
<li class="toc ulEmpty" id="section-toc.1-1.7.2.1">
                <p id="section-toc.1-1.7.2.1.1"><a href="#section-7.1" class="xref">7.1</a>.  <a href="#name-normative-references" class="xref">Normative References</a><a href="#section-toc.1-1.7.2.1.1" class="pilcrow">¶</a></p>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.7.2.2">
                <p id="section-toc.1-1.7.2.2.1"><a href="#section-7.2" class="xref">7.2</a>.  <a href="#name-informative-references" class="xref">Informative References</a><a href="#section-toc.1-1.7.2.2.1" class="pilcrow">¶</a></p>
</li>
</ul>
</li>
<li class="toc ulEmpty" id="section-toc.1-1.8">
            <p id="section-toc.1-1.8.1"><a href="#section-appendix.a" class="xref"></a><a href="#name-authors-address" class="xref">Author's Address</a><a href="#section-toc.1-1.8.1" class="pilcrow">¶</a></p>
</li>
</ul>
</nav>
</section>
</div>
<div id="introduction">
<section id="section-1">
      <h2 id="name-introduction">
<a href="#section-1" class="section-number selfRef">1. </a><a href="#name-introduction" class="section-name selfRef">Introduction</a>
      </h2>
<p id="section-1-1">TLS 1.2 <span>[<a href="#RFC5246" class="xref">RFC5246</a>]</span> and earlier
      versions of TLS support renegotiation, a mechanism for changing
      parameters and keys partway through a connection. This was sometimes
      used to implement reactive client authentication in HTTP/1.1 <span>[<a href="#RFC7230" class="xref">RFC7230</a>]</span>, where the server decides whether or
      not to request a client certificate based on the HTTP request.<a href="#section-1-1" class="pilcrow">¶</a></p>
<p id="section-1-2">HTTP/2 <span>[<a href="#RFC7540" class="xref">RFC7540</a>]</span> multiplexes multiple
      HTTP requests over a single connection, which is incompatible with the
      mechanism above. Clients cannot correlate the certificate request with
      the HTTP request that triggered it. Thus, <span><a href="https://www.rfc-editor.org/rfc/rfc7540#section-9.2.1" class="relref">Section 9.2.1</a> of [<a href="#RFC7540" class="xref">RFC7540</a>]</span> forbids renegotiation.<a href="#section-1-2" class="pilcrow">¶</a></p>
<p id="section-1-3">TLS 1.3 <span>[<a href="#RFC8446" class="xref">RFC8446</a>]</span> removes
      renegotiation and replaces it with separate post-handshake
      authentication and key update mechanisms. Post-handshake authentication
      has the same problems with multiplexed protocols as TLS 1.2
      renegotiation, but the prohibition in <span>[<a href="#RFC7540" class="xref">RFC7540</a>]</span> only applies to renegotiation.<a href="#section-1-3" class="pilcrow">¶</a></p>
<p id="section-1-4">This document updates HTTP/2 <span>[<a href="#RFC7540" class="xref">RFC7540</a>]</span> to similarly forbid TLS 1.3 post-handshake
authentication.<a href="#section-1-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="requirements-language">
<section id="section-2">
      <h2 id="name-requirements-language">
<a href="#section-2" class="section-number selfRef">2. </a><a href="#name-requirements-language" class="section-name selfRef">Requirements Language</a>
      </h2>
<p id="section-2-1">
    The key words "<span class="bcp14">MUST</span>", "<span class="bcp14">MUST NOT</span>",
    "<span class="bcp14">REQUIRED</span>", "<span class="bcp14">SHALL</span>", "<span class="bcp14">SHALL NOT</span>", "<span class="bcp14">SHOULD</span>", "<span class="bcp14">SHOULD NOT</span>",
    "<span class="bcp14">RECOMMENDED</span>", "<span class="bcp14">NOT RECOMMENDED</span>",
    "<span class="bcp14">MAY</span>", and "<span class="bcp14">OPTIONAL</span>" in this document are
    to be interpreted as described in BCP 14 <span>[<a href="#RFC2119" class="xref">RFC2119</a>]</span>
        <span>[<a href="#RFC8174" class="xref">RFC8174</a>]</span> when, and only when, they appear in all capitals,
    as shown here.<a href="#section-2-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="post-handshake-authentication-in-http2">
<section id="section-3">
      <h2 id="name-post-handshake-authenticati">
<a href="#section-3" class="section-number selfRef">3. </a><a href="#name-post-handshake-authenticati" class="section-name selfRef">Post-Handshake Authentication in HTTP/2</a>
      </h2>
<p id="section-3-1">HTTP/2 servers <span class="bcp14">MUST NOT</span> send post-handshake TLS 1.3 CertificateRequest messages.
HTTP/2 clients <span class="bcp14">MUST</span> treat such messages as connection errors (see <span><a href="https://www.rfc-editor.org/rfc/rfc7540#section-5.4.1" class="relref">Section 5.4.1</a> of [<a href="#RFC7540" class="xref">RFC7540</a>]</span>) of type PROTOCOL_ERROR.<a href="#section-3-1" class="pilcrow">¶</a></p>
<p id="section-3-2"><span>[<a href="#RFC7540" class="xref">RFC7540</a>]</span> permitted renegotiation before the HTTP/2 connection preface to
provide confidentiality of the client certificate. TLS 1.3 encrypts the client
certificate in the initial handshake, so this is no longer necessary. HTTP/2
servers <span class="bcp14">MUST NOT</span> send post-handshake TLS 1.3 CertificateRequest messages before
the connection preface.<a href="#section-3-2" class="pilcrow">¶</a></p>
<p id="section-3-3">The above applies even if the client offered the
      <code>post_handshake_auth</code> TLS extension. This extension is advertised
      independently of the selected Application-Layer Protocol Negotiation
      (ALPN) protocol <span>[<a href="#RFC7301" class="xref">RFC7301</a>]</span>, so it is not
      sufficient to resolve the conflict with HTTP/2. HTTP/2 clients that also
      offer other ALPN protocols, notably HTTP/1.1, in a TLS ClientHello
      <span class="bcp14">MAY</span> include the <code>post_handshake_auth</code> extension to
      support those other protocols. This does not indicate support in
      HTTP/2.<a href="#section-3-3" class="pilcrow">¶</a></p>
</section>
</div>
<div id="other-post-handshake-tls-messages-in-http2">
<section id="section-4">
      <h2 id="name-other-post-handshake-tls-me">
<a href="#section-4" class="section-number selfRef">4. </a><a href="#name-other-post-handshake-tls-me" class="section-name selfRef">Other Post-Handshake TLS Messages in HTTP/2</a>
      </h2>
<p id="section-4-1"><span>[<a href="#RFC8446" class="xref">RFC8446</a>]</span> defines two other messages that are exchanged after the handshake is
complete: KeyUpdate and NewSessionTicket.<a href="#section-4-1" class="pilcrow">¶</a></p>
<p id="section-4-2">KeyUpdate messages only affect TLS itself and do not require any interaction
with the application protocol. HTTP/2 implementations <span class="bcp14">MUST</span> support key updates
when TLS 1.3 is negotiated.<a href="#section-4-2" class="pilcrow">¶</a></p>
<p id="section-4-3">NewSessionTicket messages are also permitted. Though these interact
      with HTTP when early data is enabled, these interactions are defined in
      <span>[<a href="#RFC8470" class="xref">RFC8470</a>]</span> and are allowed for in the
      design of HTTP/2.<a href="#section-4-3" class="pilcrow">¶</a></p>
<p id="section-4-4">Unless the use of a new type of TLS message depends on an interaction
      with the application-layer protocol, that TLS message can be sent after
      the handshake completes.<a href="#section-4-4" class="pilcrow">¶</a></p>
</section>
</div>
<div id="security-considerations">
<section id="section-5">
      <h2 id="name-security-considerations">
<a href="#section-5" class="section-number selfRef">5. </a><a href="#name-security-considerations" class="section-name selfRef">Security Considerations</a>
      </h2>
<p id="section-5-1">This document resolves a compatibility concern between HTTP/2 and TLS 1.3 when
supporting post-handshake authentication with HTTP/1.1. This lowers the barrier
for deploying TLS 1.3, a major security improvement over TLS 1.2.<a href="#section-5-1" class="pilcrow">¶</a></p>
</section>
</div>
<div id="iana-considerations">
<section id="section-6">
      <h2 id="name-iana-considerations">
<a href="#section-6" class="section-number selfRef">6. </a><a href="#name-iana-considerations" class="section-name selfRef">IANA Considerations</a>
      </h2>
<p id="section-6-1">This document has no IANA actions.<a href="#section-6-1" class="pilcrow">¶</a></p>
</section>
</div>
<section id="section-7">
      <h2 id="name-references">
<a href="#section-7" class="section-number selfRef">7. </a><a href="#name-references" class="section-name selfRef">References</a>
      </h2>
<section id="section-7.1">
        <h3 id="name-normative-references">
<a href="#section-7.1" class="section-number selfRef">7.1. </a><a href="#name-normative-references" class="section-name selfRef">Normative References</a>
        </h3>
<dl class="references">
<dt id="RFC2119">[RFC2119]</dt>
<dd>
<span class="refAuthor">Bradner, S.</span>, <span class="refTitle">"Key words for use in RFCs to Indicate Requirement Levels"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 2119</span>, <span class="seriesInfo">DOI 10.17487/RFC2119</span>, <time datetime="1997-03">March 1997</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc2119">https://www.rfc-editor.org/info/rfc2119</a>&gt;</span>. </dd>
<dt id="RFC5246">[RFC5246]</dt>
<dd>
<span class="refAuthor">Dierks, T.</span><span class="refAuthor"> and E. Rescorla</span>, <span class="refTitle">"The Transport Layer Security (TLS) Protocol Version 1.2"</span>, <span class="seriesInfo">RFC 5246</span>, <span class="seriesInfo">DOI 10.17487/RFC5246</span>, <time datetime="2008-08">August 2008</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc5246">https://www.rfc-editor.org/info/rfc5246</a>&gt;</span>. </dd>
<dt id="RFC7230">[RFC7230]</dt>
<dd>
<span class="refAuthor">Fielding, R., Ed.</span><span class="refAuthor"> and J. Reschke, Ed.</span>, <span class="refTitle">"Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing"</span>, <span class="seriesInfo">RFC 7230</span>, <span class="seriesInfo">DOI 10.17487/RFC7230</span>, <time datetime="2014-06">June 2014</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7230">https://www.rfc-editor.org/info/rfc7230</a>&gt;</span>. </dd>
<dt id="RFC7301">[RFC7301]</dt>
<dd>
<span class="refAuthor">Friedl, S.</span><span class="refAuthor">, Popov, A.</span><span class="refAuthor">, Langley, A.</span><span class="refAuthor">, and E. Stephan</span>, <span class="refTitle">"Transport Layer Security (TLS) Application-Layer Protocol Negotiation Extension"</span>, <span class="seriesInfo">RFC 7301</span>, <span class="seriesInfo">DOI 10.17487/RFC7301</span>, <time datetime="2014-07">July 2014</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7301">https://www.rfc-editor.org/info/rfc7301</a>&gt;</span>. </dd>
<dt id="RFC7540">[RFC7540]</dt>
<dd>
<span class="refAuthor">Belshe, M.</span><span class="refAuthor">, Peon, R.</span><span class="refAuthor">, and M. Thomson, Ed.</span>, <span class="refTitle">"Hypertext Transfer Protocol Version 2 (HTTP/2)"</span>, <span class="seriesInfo">RFC 7540</span>, <span class="seriesInfo">DOI 10.17487/RFC7540</span>, <time datetime="2015-05">May 2015</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc7540">https://www.rfc-editor.org/info/rfc7540</a>&gt;</span>. </dd>
<dt id="RFC8174">[RFC8174]</dt>
<dd>
<span class="refAuthor">Leiba, B.</span>, <span class="refTitle">"Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words"</span>, <span class="seriesInfo">BCP 14</span>, <span class="seriesInfo">RFC 8174</span>, <span class="seriesInfo">DOI 10.17487/RFC8174</span>, <time datetime="2017-05">May 2017</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8174">https://www.rfc-editor.org/info/rfc8174</a>&gt;</span>. </dd>
<dt id="RFC8446">[RFC8446]</dt>
<dd>
<span class="refAuthor">Rescorla, E.</span>, <span class="refTitle">"The Transport Layer Security (TLS) Protocol Version 1.3"</span>, <span class="seriesInfo">RFC 8446</span>, <span class="seriesInfo">DOI 10.17487/RFC8446</span>, <time datetime="2018-08">August 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8446">https://www.rfc-editor.org/info/rfc8446</a>&gt;</span>. </dd>
</dl>
</section>
<section id="section-7.2">
        <h3 id="name-informative-references">
<a href="#section-7.2" class="section-number selfRef">7.2. </a><a href="#name-informative-references" class="section-name selfRef">Informative References</a>
        </h3>
<dl class="references">
<dt id="RFC8470">[RFC8470]</dt>
<dd>
<span class="refAuthor">Thomson, M.</span><span class="refAuthor">, Nottingham, M.</span><span class="refAuthor">, and W. Tarreau</span>, <span class="refTitle">"Using Early Data in HTTP"</span>, <span class="seriesInfo">RFC 8470</span>, <span class="seriesInfo">DOI 10.17487/RFC8470</span>, <time datetime="2018-09">September 2018</time>, <span>&lt;<a href="https://www.rfc-editor.org/info/rfc8470">https://www.rfc-editor.org/info/rfc8470</a>&gt;</span>. </dd>
</dl>
</section>
</section>
<div id="authors-addresses">
<section id="section-appendix.a">
      <h2 id="name-authors-address">
<a href="#name-authors-address" class="section-name selfRef">Author's Address</a>
      </h2>
<address class="vcard">
        <div dir="auto" class="left"><span class="fn nameRole">David Benjamin</span></div>
<div dir="auto" class="left"><span class="org">Google LLC</span></div>
<div class="email">
<span>Email:</span>
<a href="mailto:davidben@google.com" class="email">davidben@google.com</a>
</div>
</address>
</section>
</div>
<script>var toc = document.getElementById("toc");
var tocToggle = toc.querySelector("h2");
var tocNav = toc.querySelector("nav");

// mobile menu toggle
tocToggle.onclick = function(event) {
    if (window.innerWidth < 1024) {
 var tocNavDisplay = tocNav.currentStyle ? tocNav.currentStyle.display : getComputedStyle(tocNav, null).display;
 if (tocNavDisplay == "none") {
     tocNav.style.display = "block";
 } else {
     tocNav.style.display = "none";
 }
    }
}

// toc anchor scroll to anchor
tocNav.addEventListener("click", function (event) {
    event.preventDefault();
    if (event.target.nodeName == 'A') {
 if (window.innerWidth < 1024) {
     tocNav.style.display = "none";
 }
 var href = event.target.getAttribute("href");
 var anchorId = href.substr(1);
 var anchor =  document.getElementById(anchorId);
 anchor.scrollIntoView(true);
 window.history.pushState("","",href);
    }
});

// switch toc mode when window resized
window.onresize = function () {
    if (window.innerWidth < 1024) {
 tocNav.style.display = "none";
    } else {
 tocNav.style.display = "block";
    }
}
</script>
</body>
</html>

